High speed pulse counting circuits



R. E. NATHER HIGH SPEED PULSE COUNTING CIRCUITS April 14, 1959 Filed Jan. 27, 1955 INVENTOR ROY E. NATI-1ER ATTONEY.

O. madrm mmJDa HIGH SPEED PULSE 'COUNTING CIRCUITS Roy VE. Nather, Walnut lCreek, lCalif., assignor, by mesne assignments, to the United States of America as representedlby theUuited States Atomic lEnergyCommission Application January i27, 1955, Serial No..484,601

Claims. y(Cl. S15-*8.5)

The present invention relatesgenerally to counting circuits and more particularly to a high frequency decade scaling counter.

In many instances uit is more desirable to utilizedecade scaling circuits for counting than the well-established binary circuits. The first decade scaling circuits were based on the binary` circuits, and the large number of tubes required tended to make the decade'circuits unreliable and excessively bulky. .For this reason, various self-contained decade counter tubes have been developed to provide compact, low maintenance counters.

One classification utilizes coldfcathode, gas-filled counting tubes. There are several advantages .to this .type of counter tube when they are used at ,the lower frequencies or pulse repetition rates; however, at the higher frequencies the high input capacities and. the `relativeslowness of gas-ionization processes severely limit the capabilities of the device.

Another class of decade counting tubes has been developed based on the deflectionof an electron beam. Such 'devices are potentially very fast owing to negligible beam inertia and the absence of gas ionization, the interelectrode and wiring capacities eventuallylimiting the counting rate.

The present invention is a circuit greatly extending the frequency range of the electron beam -type `of decade counting tubes. The .theory and structure of a particular tube adaptable to the present invention is disclosed in U.S. Patent No. 2,642,547 issued to'K. Rodenhuis, June 16, 1953, and the tubeis available commercially under the designation EIT.

It is an object of the present invention to provide means for counting high frequency pulses.

It is a further object of the present invention to provide means for extending the frequency range of standard counting tubes.

It is another object of the present invention to provide a counter having a very short resolving time when recording random pulses.

It is still another object ofthe present invention to provide a light weight and compact counting apparatus.

The invention, both as to its organization and method of operation, together with further objects and advantages thereof, will best be `understood by reference to the following specification taken in conjunction with the accompanying drawing in which there `is shown one preferred embodiment of the invention.

Referring now to the drawing, there is shown a decade scalar tube 11. The scalar tube 11 is a small cathode ray tube where the electron beam may be deflected and stabilized in any one of a plurality of positions. A cathode 12 of the scalar tube 11 is coupled to a ground potential bus 13 by a cathode resistor 14. In operation, the cathode 12 emits electrons which are formed into a beam by an accelerating and focusing electrode 16, which is directly connected to a B plus bus 17. The intensity of the electron beam may be regulated by a control grid 18. A voltage .divider between the B plus bus 17 and theground ICC potential bus 13 comprises `series resistorsl9, 21, and 22 with the juncture of the voltage divider resistors .121 and 22 coupled t-o thecontrol grid 18 ofthe decade-tube 11 through acurrent limiting resistor '23 for 'maintainingthe ,proper bias onthe controlgrid 18.

A rst deilection plate.24 is maintained at a constant voltage by a connection to the junction of the voltage divider resistors 19 and 21. A second delleetion plate 26 1s coupled to Vthe B plus bus 17 through a deflection plate :resistor y27 having a resistance value of the order of 1 megohm. The voltage on the second deflection plate 26 may be varied, thus deecting the electron beam as desired. At certain `values yof deflection, the electron beam Apasses through one of ten slots in a slotted electrode I258 air; a resistor 29 couples such electrode to the B plus usA Some of the electrons passing through the slotted electrode 2S will impingeon a slotted anode 31, which is connected to the second deilectionlplate 26. The remainder of the electron beam strikes a fluorescent material lined portion 32 of the envelope of the scalar tube 11 which portion is directly connected to the B plus bus 17.

The electrodes of the scalar tube 11 are constructed and positioned so that a iluorescing mark will be produced at one of ten positions. Anumber (not shown) from zero to nine at each position indicates the location of the electron beam. A feedback system hereinafter described causes the electron beam to be stable inany ofthe various positions. `By the .application of a negative voltage signal to the second deflection plate 26, the electron beam is shifted to the-next Vsuccessive position.

An input terminal 34 is 'arranged yfor convenient vconnection to the external source of voltage pulses which lare to be counted. A conventional pulseshaping circuit 36 `(shown here in Vblock form) is connected Vto theinput terminal 34 and converts input pulses into positive pulses having a preferred amplitude and duration suitable for use with the subject invention, in this instance 2() volts and 0.3 microseconds. The output of the puise shaper 36 is applied to the control grid of a pulse amplifier tube 37, a first grid resistor 38 coupling the control grid to the ground potential bus 13. p

The plate of the pulse amplifier tube 37 is vdirectly connected t'o the second dellectionplate 26 and the'slotted anode 31 of scalar tube 11. Thus pulse signals applied at the input 34 result .in an amplified negative pulse at the second deflection 'plate 26 and the electron beam is stepped to the next successive position.

With each successive position of the electron beam, the slot size in the slotted electrode 28 is increased, al-

lowing moreof the beam to impinge on .the slotted 'anode 31. Thus as the beam is stepped from thezero position to the nine position the `number Vof .electrons .impinging on the slotted anode 31 .is gradually increased with leach step. The voltage drop across the l megohm deflection.

plate resistor v27 causes the second deilection plate'26 to have a less positive voltage Witheach step, thus stabilizing the beam at each position. The electron `beam Vis nearest the second dellection plate 26 at the zero position and increasingly further away at the subsequent positions.

When the electron beam is -in the ninth position, a succeeding pulse causes the electron beam to strike a reset anode 39 and rapidly returns the electron beam to the zero position. ASuch `action is accomplished by returning the second deflection plate 26 to a maximum positive voltage. To accomplish the above operation, previous circuits have relied upon the application of a negative bias to the control grid 18, thus cutting off `the electron beam. The negative charge on the second dellection plate 26 was allowed to discharge, the time required for the discharge depending upon the resistance of the deflection plate yresistor 27 and `the interelectrode tities may be changed, the scalar tube being vdesigned to operate with a 1 megohm value for the deflection plate resistor 27. l g

The reset anode 39 is Vcoupled-to the B plus busv 17 through a reset anode resistor 41. A reset anode coupling capacitor 42 is connected between the control grid of a reset pulse amplifying tube 43 and the reset anode 39. The cathode of thepulse amplifying tubev 43 is coupled to the ground bus 13 through a cathode resistor 44 connected in parallel with a cathode capacitor 46. The reset pulse amplifying tube 43 is maintained in a conducting state by coupling the control grid to the cathode through a grid resistor 47. The voltage developed across the cathode resistor 44 is utilized by the pulse amplifying tube 37 as grid bias, and a cathode resistor 48 couples the cathode of the pulse amplifying tube 37 to the cathode of the reset pulse amplifying tube 43.

The anode of the reset pulse amplifying tube 43 is coupled to the B plus bus 17 through an anode resistor 49. The application of a negative pulse to the grid of the reset pulse amplifying tube 43 causes an amplified positive pulse at the anode which is coupled through a coupling capacitor 51 to the control grid of an output tube S2. A voltage divider between the B plus bus 17 and the ground bus 13 comprises a resistor 53 in series with a bias potentiometer 54. The adjustable arm of the potentiometer 54 is coupled to the control grid of the output tube 52 through a parallel-connected grid bias resistor 56 and bias diode 57 with the cathode electrode of the diode being connected to the control grid of the output tube. grid of the output tube 52 can never become lower in voltage than the voltage selected by the bias potentiometer 54, thus`damping any tendency for oscillation and spurious counts.

The plate of the output tube 52 is coupled to the B plus bus 17 through a plate resistor 58 and is also coupled to the control grid of a univibrator tube 59 through a coupling capacitor 61. An output coupling capacitor 62 connects the plate of the output tube 52 to by the pulse amplifier tube 37 and applied as a negativegoing voltage pulse to the second deflection plate 26 of the scalar tube 11. The electron beam in the scalar tube 11 is deflected by the"negative pulse and stabilizes in the next successive position. 'I'he electron beam is now passing through a larger slot in the slotted electrode 28 than when in the previous position, therefore more electrons are impinging `on the slotted anode 31. More current isflowing through the slotted anode resistor 27 and a less. positive voltage is maintained at the second deflection plate 26 than when the electron beam was in the previous position. Thus, the electron beam is stabilized in the newposition. As the electron beam adi vances from Athe zero to the ninth position the voltage I may be of lower amplitude as the second deflection plate Such arrangement insures that the control 26 voltage decreases. The reset pulse amplifying tube 43 conducts enough current so that the voltage developed across ythe cathode resistor 44 will bias the pulse amplifier tube 37 to cut off except when input pulses are applied. Thus, the voltage at the second deflection plate 26 is determined solely by the electrons impinging on the slotted anodel 31.

When the electron beam is stepped from the ninth position to strike the reset anode 39, a negative pulse is applied to the control grid of the reset pulse amplifying tube 43. An amplified positive pulse from the plate of the reset pulse amplifying tube 43 is coupled to the control grid of the output tube 52.

An amplified negative pulse at the plate of the output tube 52 is applied both to the output terminal 63 and voltage at the second deflection plate 26, thus the disan output terminal 63, suitable for connection to a succeeding decade circuit, since an output pulse is provided at the output terminal 63 for every tenth pulse applied at the input terminal 34.

To control the time necessary for the coupling capacitor 61 to discharge after the application of a voltage pulse, a grid potentiometer is connected at one end to the grid of the tube 59 with the adjustable arm of the potentiometer connected to the other end thereof and coupled to the B plus bus 17 through a voltage divider resistor 66 while a decoupling capacitor 67 and a parallel resistor 68 couple the adjustable arm of the grid potentiometer 64 to the ground bus 13.

The cathode of the univibrator tube 59 and the cathode of the output tube 52 are directly connected together and coupled to the ground bus 13 through a common cathode resistor 69. The plate of the univibrator tube 59 is coupled to the B plus bus 17 through a diode resistor 71. The plate of a discharge diode 72 is directly connected to the plate of the univibrator tube 59. The cathode of the discharge diode 72 is connected to the second deflection plate 26 of the scalar tube 11. The resistance value of the diode resistor 71 is chosen so that the voltage at the second deflection plate 26 of the scalar tube 11 is normally more positive than the voltage at the plate of the univibrator tube 59. Thus the discharge diode 72 will not conduct until a negative voltage is applied to the control grid/of the univibrator tube 59.

To summarize the operation of the device, assume that voltage pulses from an external vsource are being applied to the input terminal 34 and the pulse Shaper 36 modifies the pulses so 'that they'are uniform in voltage and duration.- The'output of the pulse shaper 36 is amplified charge diode does not conduct. But with a negative pulse applied to the grid, the univibrator tube S9 stops conducting and the plate voltage approaches the voltage value of the B plus bus 17. The discharge diode 72 starts conducting and effectively places the diode resistor 71 in parallel with the deflection plate resistor 27. Since the resistance of the diode resistor 71 is relatively low (9000 ohms in this instance) the second deflection plate 26 quickly assumes a positive voltage and the electron beam of the scalar tube 11 is rapidly returned to the zero position. The time period during which the univibrator tube 59 conducts is adjustable by varying the grid potentiometer 64.

The circuit here described is capable of counting rates over one megacycle, the limiting factor being the reset function which is accomplished in about 0.8 microseconds. In the counting of random pulses the pulse shaper 36 may be arranged so that two or more input pulses occurring at the same time are presented to the control grid of the pulse amplifier tube 37 as a single pulse with multiple amplitude and the electron beam will be stepped two or more positions. Thus the effective resolving time of the circuit may be quite low.

While the invention has been disclosed with respect to a single preferred embodiment, it will be apparent to those skilled in the art that numerous variations and modifications may be made within the spirit and scope of the invention and thus it is not intended to limit the invention except as defined in the following claims.

What is claimed is:

l. In an electronic circuit having a vacuum tube of the type characterized by an electron beam and a deflection electrode to sequentially deflect said electron beam into one of a plurality of predetermined positions and a reset anode positioned to intercept said electron beam at one of said predetermined positions, the combination comprising a potential source, a resistance connected from said deection electrode to said potential source, a diode switch circuit coupled in parallel with said resistance, an amplifying circuit coupled from said reset anode to said diode, said diode being rendered conductive when said reset anode intercepts said electron beam.

2. In an electronic counting circuit having a vacuum tube of the type characterized by an electron beam, a deflecting electrode to sequentially deect said electron beam into one of a plurality of predetermined positions, a reset anode positioned to intercept said electron beam at one of said predetermined positions, the combination comprising a source of potential, a resistor coupling said deecting electrode to said source of potential, a normally open switch coupled from said deilection electrode to said source of potential, an amplifier responsive to potential changes of said reset anode, and control means closing said switch in response to signals received from said amplifier.

3. In a counting circuit, the combination comprising a vacuum tube having an electron beam and a beam dcecting plate, a potential source, a discharge resistor coupling said beam deecting plate to said potential source, a diode coupled to said beam deflecting plate, a diode resistor coupling said diode to said potential source, a beam intercepting anode disposed in said vacuum tube, a univibrator tube having -a plate connected to the juncture of said diode and said diode resistor, and an amplitier coupling said beam intercepting anode to a control electrode of said univibrator tube, said diode being rendered conductive when said electron beam impinges on said beam intercepting diode.

4. In an electronic circuit, the combination comprising a vacuum tube having an electron beam and a beam deecting plate, a source of positive potential, a discharge resistor coupling said beam deecting plate to said source of positive potential, a diode having a cathode coupled to said beam deecting plate, a diode resistor coupling the anode of said diode to said source of positive potential, a beam interrupting anode of said vacuum tube, a normally conducting univibrator tube having a plate connected to the juncture of the anode of said diode and said diode resistor, and an amplifier coupling negative pulses from said beam interrupting anode to a control electrode of said univibrator tube for rendering the latter non-conductive when said electron beam impinges on said beam interrupting anode.

5. In an electronic counting circuit, the combination comprising a scaler tube of the class having an, electron beam deflecting electrode and a beam intercepting reset anode, a potential source, a discharge resistor coupled from said deecting electrode to said potential source, a diode resistor having substantially lower resistance than said discharge resistor and having one end connected to said potential source, a diode having an anode connected to the other end of said diode resistor and having a cathode connected to said beam deecting electrode, a normally conducting pulse amplier tube having a control electrode coupled to said reset anode and having an anode connected to the anode of said diode, said amplier tube being rendered non-conductive when said electron beam is intercepted by said reset anode.

References Cited in the tile of this patent UNITED STATES PATENTS 2,555,999 Ringlee June 5, 1951 2,568,449 Hansen Sept. 18, 1951 2,571,723 Gonker Oct. 16, 1951 2,591,981 Overbeek Apr. 8, 1952 2,657,330 Hepp Oct. 27, 1953 2,712,570 De Polder July 5, 1955 2,736,803 Hugenholtz Feb. 28, 1956 OTHER REFERENCES Electronic Engineering, February 1954, pages 59-61, Decimal Counting Tubes, Kandiah. 

